Quick Links

moved-one piece of oak baseboard or flooring, for instance-this would be the preferred method. Small articles, such as an antique tool or a picture frame, may be heated in a kiln or placed in a freezer where rapid temperature change does most of the killing. Rapid temperature change is not 100% successful, though, and obviously, some valuables cannot withstand the chilling or heating process. If the infestation is widespread, fumigating may be called for. Methyl bromide is the preferred chemical because it will kill all life stages including eggs. This is an expensive treatment that needs to be handled by a professional pest-control company, and the cost must be balanced against the cost of replacing the wood. Proper fumigating will kill all insects present, but does nothing to guarantee or prevent the wood from reinfestation. Infested lumber can also be fumigated under a tarp. Small articles or furniture can be treated in a fumigation vault or chamber. Painting or sealing the wood will prevent it from becoming infested if all pores are plugged, but it will not control an ongoing infestation by itself. Adult females will use existing emergence holes as a way of getting back into the wood (unless you've somehow managed to plug them all) , and once inside, they can find pore spaces in which to lay their eggs. The final treatment alternative is to treat the surface of the infested wood with an insecticide. By placing a thin layer of chemical on the outer surface, adults and larvae that come into contact with the treated surface will be killed, but any larvae living deep in the wood will not be affected. This surface treatment helps to prevent reinfestation and over time will "bleed out" the population. The infestation will remain active for some time after treatment, and even if the adults are killed upon emerging, they still produce exit holes. Proper coverage is also of great concern with surface treatment. Spraying the outer surface of baseboards or the top surface of flooring leaves the undersurface of the wood untreated and gives the beetles continued access to the wood. At present there are only a small number of materials registered for surface treatment of powderpost beetles indoors. Two formulations of chlorpyrifos (Dursban), some of the new termiticides and a formulation of silica gel/pyrthrum are labeled for wood-infesting beetles. In the past some formulations of pentachlorphenol were used, but they are no longer available for indoor treatment of existing structures. Chemicals can be sprayed or painted on in- fested wood. Formulations with oil or petroleum solvents as carriers do a better job of penetrating the wood surface than do water-based materials. One of the major problems is that the best formulations for treating wood inside buildings are not available to the homeowner. Either you must hire a professional or settle for the shorter residual formulations. Read the labels carefully for proper use. Anobiid beetles cies of deathwatch beetles (family Anobiidae) in the U. S. Several species attack and reinfest seasoned wood, and they are commonly lumped in with the powderpost beetles. Attacks often start in cold, unventilated crawl spaces and spread to other parts of the house. Anobiids attack the sapwood of both hardwoods and softwoods, and can extend into the heartwood. In nature, these beetles breed in old, dried limbs of trees. Anobiids range from - and are usually reddish-brown to grey in color. They have a distinctive hood-like bellshaped thorax, which conceals the head when viewed from above. Adult females lay up to fifty eggs in the cracks in wood or in old emergence holes. They prefer rough-sawn lumber, and the females may be inhibited from laying eggs on smooth or finished wood. Anobiids have a high moisture require- VIO in. to 12 ment. Their eggs will not hatch at humidity below 60%. Larvae (immature beetles) are greyish-white wormlike grubs with black jaws. Larval development may take from one to ten years or more, depending on the species of beetle and the nutritional content of the wood. There are documented cases of anobiids taking 25 years to emerge from pieces of furniture. The obvious sign of an infestation is the accumulation of powdery frass and tiny pellets found underneath infested wood. Fresh powder is bright and light-colored like freshly sawn wood. Small V2s-in. long oval pellets will fall from infested channels or old emergence holes. These pellets will give the frass a gritty quality and will be loosely packed in the tunnels. This powder will not be as fine as that left by the Iyctid beetles. If all the frass appears yellowed and partially caked on the surface where it lies, the infestation has died out. Emergence holes will be round and from in. to VB in. in diameter. 1;\6 in. in size There are over 260 spe- It normally takes 10 or more years for the number of beetles to become large enough for the infestation to be noted. As mentioned earlier, high-moisture conditions in wood are more attractive to adults and allow for shorter generation times. Old unheated buildings, livestock housing and homes with an earthen basement or damp crawl space are most susceptible to attack. Wood with a moisture content of 13% to 30% is needed for survival. Anobiids are much more likely to infest old lumber and wood than are the other species of wood-infesting beetles. Controlling anobiid beetles options for anobiids are much the same as they are for the powderpost beetles, but moisture plays more of a role in the beetles' environment. Proper vapor barriers and increased ventilation in crawl spaces are very important. Where excess moisture is a problem, the first step is to correct the cause. It does, however, take wood a long time to dry out, and reducing moisture may not be enough to control an infestation. Infestations should be checked closely to - be sure the beetles are still active. If structural wood has been heavily attacked, it may have to be replaced. Probe the infested wood with an ice pick to assess damage. Remember that much of the attack will be confined to the sapwood, and if much of the beam is heartwood, it may not be susceptible to further attack. Chemical sprays such as Dursban TC can be used, or the building can be fumigated. For fumigations, methyl bromide is the product of choice because it kills all life stages. Fumigation has no residual so it will not prevent further infestations. D Phil Pellitteri directs the insect diagnostic lab of the Cooperative Extension Program of the University of Wisconsin at Madison. Photos by the author. The control Powderpost beetles attack only hardwoods like the piece of beam pictured above. They prefer porous woods with a high starch and water content. April/May 1990 69